Question

How many single bonds can a carbon atom form?

Answer 1

Four.

Explanation:

It has four electrons in its outer shell which it can use for bonding, and needs to gain four in order to fill its outer shell.
As with all covalent bonds, it will 'share one to get one' - so if it shares 4, it will get 4, which adds up to 8 & completes its outer shell.